A power divider is a commonly used circuit in electronics. It is used to split a signal into a pair of signals identical to the original. Often, it is advantageous to introduce a phase shift between the divided signals. For example, phase shifts of 90 and 180 degrees are required for circuits such as phase shifters, vector modulators, mixers, and other networks. A major problem at RF and microwave frequencies is constructing a power divider that can maintain a constant 90 or 180 degrees of phase difference between the pair of divided signals over a broad bandwidth.
Power dividers are of generally two classes: passive and active. Passive power dividers can be designed to work over octave bandwidths with acceptable phase and amplitude control. However, one of the drawbacks of passive divider circuits is signal loss. Additionally, the phase and amplitude balance tends to be sensitive to a match of input and output impedances.
Active power dividers, which use a three-terminal device such as a transistor for amplification, are less sensitive to input and output matches and can provide controllable gain. This type of power divider has been used to provide a signal split with the output signals phased equally.